The foreign secretary was accused of a "clear misuse of official statistics" by Sir David Norgrove, the chairman of the UK Statistics Authority, after repeating the £350 million a week claim.

Johnson then replied to Norgrove, accusing him of a "wilful distortion of the text of my article."

The intervention was seen as a direct challenge to Prime Minister Theresa May ahead of her key speech on Brexit in Florence on Friday.

On a visit to Canada on Monday, May rebuked Johnson, saying: "This government is driven from the front, and we're all going to the same destination."

This followed Home Secretary Amber Rudd saying that Johnson was guilty of "backseat driving" over Brexit.

Clarke, who is the Conservatives' most high-profile Europhile, accused the foreign secretary of "repeating one of the more simplistic and dishonest arguments of the hardline leavers during the referendum campaign."

He said: "Personal publicity and campaigning by the foreign secretary is actually just an irrelevant nuisance."

On Johnson's Brexit vision, he added:

"[Saying] if you stick your arms out and you will fly to the great blue yonder — that's not a policy."

Johnson has told his friends that the government should be ready to abandon negotiations as the EU will not give the UK any concessions and Brexit talks will fail, the Sun newspaper has reported.

Johnson told one friend that "nobody ever beats the EU in a negotiation" and the UK will come away from talks with a bad deal.

Another friend said: "He always makes a point of saying 'no deal is better than a bad deal' because he thinks it will be what we have to do. They [the EU] want to punish us, that has always been Boris's view, and that has now come abundantly clear from the negotiations so far."